Because cardiomyocytes in adults hardly proliferate, the loss of cardiomyocytes due to ischemic heart disease or the like results in irreversible damage. Currently, no drug or procedure clinically used exhibits efficacy in replacing a cardiac scar with a functional contractile tissue. Accordingly, a new therapy is desired for regenerating normal cardiomyocytes, and a replacement therapy has been proposed, which involves administering cardiomyocytes separately produced. In such a replacement therapy, it has been studied to administer the cardiomyocytes in a sheet form to engraft the cells in the heart of a recipient (Non Patent Literature 1 and Patent Literature 1). In addition, since the amount of the cells in the sheet is insufficient and thus expected therapeutic effect is not obtained, it is considered necessary to layer the sheet before administration (Non Patent Literature 2).
Methods are exemplified, which use fetal cardiomyocytes, myoblast cells, cardiac myoblasts derived from adipose tissue-derived stem cells, and cardiomyocytes derived from embryonic stem cells as sources for cardiomyocytes for sheet preparation (Patent Literature 2, Non Patent Literature 3, and Patent Literature 3 (Japanese Patent Application No. 2011-076235)).
However, it is not reported that the effect of administration of a myocardial sheet formed using differentiated cells derived from induced pluripotent stem cells (iPS cells) improved cardiac function.